One method of applying a colour coating to a receiving surface, for example, a sheet of paper, is to lay the paper on a uniform bed or other flat surface, and pull a bar across the paper surface to apply as a coating a bead of coloured liquid or pasty material which is put on the top of the sheet. The bead is distributed evenly over the paper surface by movement of the bar across the surface.
However, the intensity of colour on the coloured surface obtained may be uneven. This may be due to small irregularities present in the surface under the paper or a non-uniform application of ink to the sheet due to the non-uniform movement of the bar across the paper surface.
In order to overcome this problem, drawdown machines have been developed. These employ adjustable pressure bars which move on specially made drawdown surfaces. These machines are, however, expensive.